1. Field of the Invention
This invention relates to devices and methods for performing air abrasion dentistry. More specifically, the invention enables a dentist to receive both visual and tactile feedback while performing restorative dental procedures using certain types of air abrasion devices.
2. Background of the Prior Art
Air abrasion dental instruments employ a gas, usually air, which carries a stream of abrasive-laden fluid to tooth surfaces. Such a stream is directed onto a target tooth surface through a nozzle for removal of decay, preparing the teeth to receive fillings, prophylactic treatment, and the like. Air abrasion dental instruments provide advantages over conventional dental drills. These advantages include eliminating the heat, noise, and vibration produced by conventional high-speed drills. Also lessened is the need for anesthesia as well as the need to cool the drill with fluid. The general technique of treating teeth using such abrasives can be traced back to the 1950's and the work of Dr. Robert Black in U.S. Pat. No. 2,696,049.
There have been many improvements and added features in the decades following the issuance of the '049 patent in 1954. One feature of air abrasion dentistry that has remained the same for almost five decades is the fact that the nozzle which delivers abrasive particles must be held at a distance from the tooth surface. In the '049 patent, Dr. Black describes the distance the nozzle must be held from the tooth and emphasizes that better results occur when the distance is as short as possible. Although the distance is taught to be short, there must be some distance between the nozzle and the tooth. Thus, the dentist using traditional (prior art) air abrasion is experiencing a visual sensation only. This is unlike the visual and tactile feedback a dentist receives when using the tools of traditional, non-air abrasion dentistry.
Since the early days of air abrasion dentistry, many articles have been written by dentists desiring to enjoy the positive aspects of air abrasion dentistry but stymied by the fact that there is no tactile sensation to the dentist when using it.
Among these publications is a paper published in the British Medical Journal Dec. 7, 1954 by Dr. G. E. Myers entitled `The Airbrasive Technique`. An article by Dr. S. Epstein in the Journal of the American Dental Association (JADA) November 1951 entitled `Analysis of Airbrasive Procedures in Dental Practice` also expresses chagrin at the non-contact nature of air abrasion. Similar papers include `Effects of Air Abrasive in Prophylaxis` by Dr. H. D. White et al in the August 1954 issue of JADA. A paper by Dr. R Goldstein et al entitled `Air-Abrasive Technology: the New Role in Restorative Dentistry` appeared in JADA, May 1994. In this paper, Dr. Goldstein cites the lack of tactile guidance as a limitation of air abrasion dentistry.
The frustration of modem dentists with the lack of tactile feedback is a continuing problem. In the May, 1999 issue of Dentistry Today, Dr. Ronald Porth describes a technique entitles "Contact Air Abrasion". In this article, Porth explains how he uses traditional air abrasion equipment to achieve both tactile and visual feedback by moving a prior art nozzle in and out of contact with a tooth surface.
Porth's describes intermittent contact of a prior art nozzle with an irregular, non-flat tooth surface.
Porth describes various ways to move an ordinary air abrasion nozzle to allow venting while the nozzle is brought into intermittent contact with a tooth surface. Porth performed these motions not on flat tooth surfaces but on irregular molar surfaces with pits and fissures. Since they are movements in and out of contact, they are not the steady, continuous contact of a nozzle with a tooth surface taught by the instant invention. Prior to the present invention, constant contact of a prior art nozzle with a flat tooth surface terminated the cutting action of the abrasive-laden stream. There was also a likelihood that the nozzle will clog with abrasive particles or have bursts of particles when the process was restarted.
In the January 2000 issue of Dentistry Today, George Freedman comments on the lack of tactile feedback as being a negative point concerning air abrasion dentistry. The article is entitled "Ultraconservative Resin Restorations `Watch and Wait` is Not Acceptable Treatment".
When using current air abrasive dental instruments such as the Kreativ Mach 5.0, the user is instructed to hold the nozzle of the handpiece at a distance from 5-10 mm from the surface of the tooth of interest. The Mach 5.0 dental instrument and procedures for its use are described in U.S. Pat. No. 5,934,904 entitled Dental Instrument and Processes and assigned to Kreativ, Inc. and herein incorporated by reference and made a part of this application.
In the April 2000 issue of Dental Product Reports, there is a product announcement for an air abrasion device designed to provide tactile feedback. In the June, 2000 issue of Dental Product Reports there is a detailed article by Dr. V. Kim Kutsch on the same air abrasion device. The device is covered by U.S. patent application Ser. No. 09/172327 entitled "Apparatus and Method for Particle Feeding by Pressure Regulation" which is assigned to Kreativ, Inc. Disclosed therein is a particle feeding system which alters particle flow to permit limited contact to a tooth surface using a prior art air abrasion nozzle.
Air abrasion dentistry requires air movement which combines with abrasive particles to create an abrasive-laden stream that cuts tooth structure. Until the present invention, dentists were required to aim the stream of abrasive-laden fluid towards the tooth surface of interest at a finite distance away from the tooth. If a prior art nozzle is placed in direct contact with a tooth surface, the nozzle's opening is partially or completely occluded, and airflow stops. The lack of air movement stops all cutting activity. However, the air abrasion device's powder feed mechanism continues to operate with reduced airflow volume. This often causes abrasive particles to build up in the device's feed line to the handpiece. This may result in an uncontrolled burst of abrasive particles when the orifice opens again, or it may clog the nozzle with particles. Dental handpieces equipped with nozzles that can successfully perform continuous contact air abrasion and methods for their use are subjects of this invention and are described herein.